Determining structural elements of the Ukrainian Shield basement (from the experience of compiling maps of geological content)

Abstract

The article briefly reviews the survey maps of geological content published and prepared for publication over the last decades, which depict the Ukrainian Shield, including the “Overview Map of the basement of the Ukrainian Shield” scale 1:1,000,000, which was compiled by the authors in 2021. All maps differ in their methodical approaches and principles of drawing. This is due to the fact that different maps emphasize different aspects of the tectonics of the basement of the Ukrainian Shield. But in the end, all the maps clearly highlight the uniqueness of the Ukrainian Shield compared to the post-Early Precambrian folding systems. The article describes the main features of the shields of ancient platforms, which distinguish them from all other geostructures of the continents. The authors recommend highlighting on the tectonic maps of the Ukrainian Shield and shields in general the following structural elements that most clearly demonstrate the structure of the shields and their features: a) megablocks; b) structural floors of megablocks and the structural and formational complexes that make them up; c) large autonomous intrusive massifs; d) near-fault synclinal and trough structures, which have a limited distribution on the Ukrainian Shield, but are much more developed on other shields. A brief description of these structural elements, which are characteristic of all shields of ancient platforms and clearly demonstrate their similarity in general, is provided. It is shown that the regional megablocks of the Ukrainian Shield are at the same time typical in their structure and composition for other shields as well. Structural and formational complexes that make up structural floors are also typical for shields. The structural floors of the megablocks themselves correspond to the Phanerozoic (Neogean) floors according to their formal characteristics, but differ from them in their historical-geological content. Faults play an important, but not decisive, role in the structure of the Ukrainian Sea, as some researchers believe. These are only boundary faults that separate megablocks and long transmegablock faults.

Keywords

• shields
• megablocks
• structural floors
• intrusive massifs
• structural-formation complexes